Digital telephone systems are well known and have replaced the prior analog systems. All telephone switching is now accomplished digitally.
Prior art digital switches, such as the Harris Corporation 20-20.RTM. switch, are used to accomplish the routing of telephone calls, both voice and data, within a private system such as a private branch exchange ("PBX") and/or into a publicly switched telephone network ("PTSN"). Such switches are also used to provide enhanced services such as call forwarding, call waiting, conference, transfer, etc.
Such switch systems are generally installed in a cabinet configured to receive a number of telephony shelves, including:
a Common Control shelf for microprocessors, memory and floppy and hard disc drives. This shelf is responsible for call control, call tracking and database management. PA1 Telephony Control shelves for providing timing and control of the telephony switching. This shelf includes Peripheral Interface Units ("PIU"s) which provide the connections to the service units. PA1 plural shelves for Telephony Interface Units or line cards ("TIUs") which contain the trunks, lines and service units. Each of these PIU units typically services 512 telephony ports.
The communication between the Common Control and Telephony Control shelves to each of the plural TIUs in prior art switches has been by flat cable. In addition, the distance over which such cabling can be run is relatively small, e.g., 13 feet, requiring that all components of the system be co-located. It is an object of the present invention to provide a novel telephone system and method in which the amount of cabling is substantially reduced and the distance substantially increased, facilitating the location of various components of the system in widely spaced locations.
Known systems have employed specialized shelves, and the lack of component interchangeability has been an impediment to expansion of installed switches. It is accordingly an object of the present invention to provide a novel system and method utilizing modular components changeable in function by the exchange or addition of cards within the shelf.
Telephone switches generally take the form of rows and columns of shelves and maintenance and repair requires the precise identification of the shelf. It is an object of the present invention to provide a novel telephony shelf which displays an identification number.
Often, the hoods of the connectors used for the line cards of a telephony shelf are made by different manufacturers and come in non-uniform sizes and may appear in a row of 16 across the back of the shelf. The prior art has attempted to maintain the connections of the hooded connectors individually, typically by screws into the line card although Velcro straps have been used. The time and trouble to ensure closure often means that closure is not assured. It is accordingly another object of the present invention to provide a novel mechanical connector for the line cards which operates on all of the connectors present without regard to variations in size and shape or the number thereof.
In known systems, the existence of a fault is displayed on a console. However, the potentially wide distribution of the components of systems requires that each location within the system be apprised of faults within the system, and the severity thereof, without regard to the location thereof. Accordingly, it is another object of the present invention to provide a novel alarm system which provides notice of selected system faults, and the severity thereof, at each location in the system.
In known systems, the power supply cards, because of the large components mounted thereon, required considerable lateral space within the shelf, especially in a redundancy configuration requiring the insertion of two power supply cards. It is accordingly another object of the present invention to provide a novel power supply card packaged to require only one half of the vertical space of previously known cards, thus facilitating redundancy by the vertical stacking of power supply cards without sacrificing lateral space needed for line cards.
Existing systems, installed for a relatively small number of telephony ports, often have excess port service capacity but the addition of ports is very difficult. It is yet another object of the present invention to provide a novel Peripheral Transport Unit with plural Peripheral Access Modules, whereby the number of ports services by legacy switches may be readily expanded.
These and many other objects and advantages of the present invention will be readily apparent to one skilled in the art to which the invention pertains from a perusal of the claims, the appended drawings, and the following detailed description of the preferred embodiments.